Distillation systems have long been known. For example, they serve to prepare water or separate alcohol from other liquids, and are used in numerous other systems. In principle, the liquid to be distilled is evaporated while exposed to heat, so as to separate it from the residues, for example from salts or other liquids with a higher boiling point. The vapor is finally cooled in another chamber, causing it to condense into the distillate.
FIG. 1 shows a multistage distillation system 1 according to prior art. Three stages are depicted, which are each denoted by lower parentheses marked S1, S2 and S3. Stage S1 is also bordered by a dashed line up to a part that is connected with stage S2 by a heat exchanger 14, Each stage S consists of an evaporator (or evaporator) E1, E2, E3, which comprises the respective left chamber of each stage S1, S2, S3, and a condenser (or condenser) C1, C2, C3, which comprises the respective chamber of the stage S shown on the right. The evaporators and condensers all have a steam space, wherein the steam spaces of the evaporators E1, E2, E3 and condensers C1, C2, C3 of the respective same stage S1, S2, S3 are interconnected by a respective connecting steam space 6, wherein the size of this connecting steam space 6 is dimensioned in such a way that the pressure P inside of the steam spaces of this stage can be balanced out unimpededly. As a consequence, the same pressure P1, P2, P3 prevails in both chambers of each stage S1, S2, S3. In each chamber, liquid 4 is upwardly conveyed out of the chamber to a spray inlet 3, and there sprayed. The sprayed liquids 4a in the evaporators E1, E2, E3 have a slightly higher temperature than the sprayed liquids 4a of the condensers C1, C2, C3 of the respective same stage. The temperatures of the evaporators E1, E2, E3 are correspondingly slightly higher, and the temperatures of the condensers C1, C2, C3 slightly lower, than the temperatures Ts1, Ts2, Ts3 of the saturation curve for the respective steam pressure P1, P2, P3 known for the respective liquid.
For this reason, the liquid 4a sprayed in each evaporator will partially evaporate and flow into the adjacent chamber of the accompanying condenser, where it collides with the cooler drops and itself condenses again. Over time, evaporated liquid thus wanders from each evaporator into the condenser of the same stage. The distillate can there be skimmed, while new liquid can be introduced into the evaporator.
As a consequence, the first stage S1 operates with a temperature T1,1 in the evaporator E1, or with the temperature T1,2 in the condenser C1, in that the liquids 4a are sprayed into the chambers with the indicated temperatures. The adjacent chamber of the condenser C1 is the evaporator E2, which forms the second stage S2 together with the condenser C2. Accordingly, these chambers of stage S2 operate with temperatures T2,1 in the evaporator E2 and T2,2 in the condenser C2, wherein the adjoining chambers C1 and E2 are set to the same temperature. Therefore, the following applies: T1,2=T2,1. In order to achieve this temperature uniformity, the lower areas of the chambers C1 and E2 are designed as heat exchangers 14, The same holds true for chambers C2 and E3, which are also interconnected with a heat exchanger, so that the temperature T2,2 of the condenser C2 and temperature T3,1 of the evaporator E3 always keep the same temperatures.
Temperature and pressure measuring devices 26, 27 in each steam space 6 are used for process monitoring. In addition, a vacuum pump V at the end of each condensation path makes it possible to siphon away incondensable gases in the system. This is important for the process to run efficiently.
In prior art, the individual stages are only interconnected with heat exchangers, so that no exchange or flow of liquids or steam can arise between the various stages S. The stages are only connected with each other via heat exchangers. While the individual stages S do operate in different, respectively adjacent temperature ranges, each does so on its own.
In recent years, the systems were improved so as to raise the efficiencies and simplify the controllers. WO 2008/122136 describes an advantageous system according to prior art with a high efficiency. It is preferably used in the environment of heat-emitting systems, such as power plants, the released thermal energy of which can be used free of charge or inexpensively. In particular, this type of distillation system can also be given a multistage design, so as to utilize the entire provided differential temperature range, for example 50-100° C.
Available to make optimal use of the provided heat for the intended purpose are heat exchangers and other known auxiliaries, which are sufficiently known. In addition, electrical current is also required for operating such a distillation system, specifically among other things for conveying the liquids by means of pumps or operating vacuum pumps for siphoning incondensable gases. The power required for operating such systems makes up a significant portion of the overall operating costs. Therefore, the power requirement must be lowered to make the distillation system less expensive to operate.